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2014WinShotcreteEMag

2013 Outstanding Infrastructure Project Interstate 81 Safety Corridor Improvements By Albert Pugliese ODepartment of Transportation (VDOT) for the in September 2011. The coordination with theCH2M Hill Constructors was required byVDOT to attend a preliminary inspection meetingn July 15, 2010, CH2M Hill Constructors,Inc., was awarded a contract by the Virginia design-build project Interstate 81 Corridor Safety railroad can sometimes be very frustrating and Operation Improvements. Faulkner Construction unpredictable. All parties were present to ensure was the general contractor. Proshot Concrete, Inc., a timely and efficient work schedule. was awarded a contract in June 2011. All workers coming within 100 ft (300 m) of The VDOT specifications required the construc- the railroad were required to attend Norfolk tion of a mechanically stabilized earth (MSE) wall Southern’s Safety Training Class. In addition, all with use of rock bolts and shotcrete. The project’s employers must provide their employees E-Rail purpose was to rebuild the north- and southbound Certification cards. This is essentially a Homeland bridge over Norfolk Southern main rail lines due to Security background check, required well in aging of the bridges and lack of clearance for the advance of the project’s start date. All personnel railroad. The first phase of the project was to widen were required to carry the E-Rail Certification the lanes for truck traffic; then, the rock bolts were card at all times. installed and shotcrete was applied. The final MSE Prior to mobilization, all submittals of rock wall was approximately 150 ft (46 m) long and bolts/grout, reinforcing steel, shotcrete mixture nearly 28 ft (9 m) high and required over 200 yd3 designs, and work schedule were required. The (153 m3) of shotcrete. rock bolts were provided by Williams Form The project was bid in two phases: Phase 1 Engineering, as well as the testing equipment from station 96+09 to 97+97 and Phase 2 from required for “pull” load testing. 96+97 to 97+56. Once the excavation was com- Proshot Concrete, Inc., started Phase I on plete, the layout for the rock bolts was determined October 24, 2011. The drill rig (Flexiroc T35) and guide wires were installed. provided by Atlas Copco arrived a few days later, once the bolt pattern and layout were complete. The drill had to be able to drill at a 90-degree angle due to clearance of the railroad track. The rock excavator drilled and blasted rock to even the plane as close as possible. The excavation was conducted in three lifts to allow a stabilized area for the rock drill. The excavation depths were 12, 9, and 11 ft (3.7, 2.7, and 3.4 m). Prior to drilling the rock-bolt holes, shotcrete was applied in varying thicknesses to the surface to help stabilize the drilling operation. The rock bolt holes were to be drilled on 6 ft (1.8 m) centers between the abutment caissons. The rock bolts ranged from 15 to 30 ft (4.5 to 9 m) in depth. Most of the bolt lengths were changed to 30 ft (9 m), as additional soil borings were obtained. The drill shafts were 3 in. (75 mm) in diameter and 1 in. (25 mm) diameter galvanized rock bolts were used with centralizers every 10 ft (3 m). The rock bolts were secured in the drilled holes with high- Fig. 1: Drain board and weep pipes were incorporated before applying strength cementitious grout. Each bolt required a the shotcrete to allow for drainage specific “pull” load test. 22 Shotcrete • Winter 2014


2014WinShotcreteEMag
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